The present invention concerns a method for controlling the reeling of a paper web or equivalent, in which the web is reeled by supporting the roll that is being formed on its circular, cylindrical outer surface by means of at least two supporting members. A first one of the supporting members in a direction of arrival of the web, is a carrier roll with the web being passed over a sector thereof to the reeling. This carrier roll forms a reeling nip with the roll being formed, which supports the roll being formed from below. Furthermore, a press member is situated at an opposite, upper side of the paper roll being formed, this press member preferably being a press roll, by means of which the roll being formed is stably maintained in reeling position.
In the forming of paper rolls reeled while supporting the same at the circumference thereof, a problem has been internal damage in the large and heavy rolls. This damage is produced, in particular, underneath the surface layer. Some of the most common damage involves crepe wrinkles in a transverse direction of the web, and web cracking. A principal cause of the damage has been ascertained to be an excessibly high nip pressure between the paper roll and the carrier roll, resulting from the weight of the paper roll or from an excessive press-roll loading.
In order for a roll of good quality to be obtained by means of a carrier-roll reel-up, it has been noted that linear load between the paper roll and the carrier roll should be about 1 to 4 kN/m. Within this range of linear load, it is possible as a rule to accomplish the desired distribution of tension in the roll.
When a carrier roll of a short radius is used, the above range of linear loading is exceeded at the final stage of reeling with large rolls that are wound, whereby the contact pressure rises to a level higher than that tolerated by a printing-paper roll. This results from a narrow nip area between the paper roll and the carrier roll. In a manner known in the prior art, attempts have been made to eliminate this problem by making the carrier roll larger, which increases the cost of manufacture and operation of the reel-up.
A soft-faced carrier roll is known from Finnish patent application No. 843184, in which the nip face becomes larger. However, a drawback therein is the dynamic problem of formation of two faces, as well as the generation of heat during the reeling.
Attempts have also been made to solve these problems by dividing the load on carrier rolls of different sizes or on inclined carrier rolls. Distribution of the load between rolls does not reduce the maximum pressure, but it increases the pressure between one of the carrier rolls and the paper roll depending on the diameter and on the inclination. The most uniform distribution of the roll pressure is obtained with equally large carrier rolls situated symmetrically underneath the paper roll, by using the construction known from U.S. Pat. No. 4,456,190.